The present invention pertains to enriched unsaturated fatty acid-containing triacylglycerols and a method of making them employing menhaden oil (MO) or partially hydrogenated menhaden oil (PHMO). In particular, the method involves the solvent fractionation of MO or PHMO to provide a lipid composition containing enriched amounts of unsaturated fatty acid esters (UFA or UFAs) including monounsaturated fatty acid esters (MUFA or MUFAs) and polyunsaturated fatty acid esters (PUFA or PUFAs).
One established approach to reducing plasma cholesterol levels is to consume a large proportion of dietary triglycerides as polyunsaturated fatty acid (PUFA) derivatives. The most widely occurring dietary PUFA is linoleic acid (C18:2n-6, or 9,12-octadecadienoic acid), which constitutes more than half of the fatty acid triglycerides of corn, soy, and safflower vegetable oils. The cholesterol lowering ability of PUFAs is believed to result from increased LDL receptor activity. See Spady and Dietschy, Proc. Nat. Acad. Sci. USA, Vol. 82 (1985), pp.4526-4530. This well established lowering of plasma LDL cholesterol concentration when PUFAs are substituted for dietary saturated fatty acids (hereinafter SFA or SFAs) provides the rationale for the widespread substitution of a variety of vegetable oils for animal fats in cooking and food formulations. The American Heart Association in its Phase I and Phase II Recommended Diets has approved the use of PUFAs as part of a large scale dietary modification for the purpose of lowering cholesterol levels in the general population. See, e.g., S. M. Grundy, Disorders of Lipids and Lipoprotein, in Internal Medicine, Stein, ed., (2nd ed. 1987), pp. 2035-2046.
However, PUFAs have significant deleterious health consequences as well as beneficial ones. Several negative effects of PUFAs may be ascribed to their increased rate of reaction via free-radical mechanisms. See, e.g., B. Halliwell and J. Gutteridge, xe2x80x9cLipid Peroxidation,xe2x80x9d Ch. 4 in Free Radicals in Biology and Medicine (2d ed. 1989). PUFAs usually have two vinylic groups separated by a methylene carbon, as is exemplified by the 9,12 diene structure of linoleic acid. Their susceptibility to peroxidation and cross-linking reactions implicates PUFAs in several undesirable processes such as tissue aging, tumorigenesis and lowering the level of beneficial HDL cholesterol as well as the level of harmful LDL cholesterol.
Monounsaturated fatty acids, such as oleic acid (C18:1n-9) or (cis-9-octadecenoic acid), are known to reduce blood cholesterol levels in non-hypertriglyceridemic individuals (F. H. Mattson and S. M. Grundy, J. Lipid Res., 26, 1985, pp. 94-202). Among vegetable oils, those of olive, peanut, rapeseed and canola have been identified as being rich sources of MUFA, with the latter type fatty acids constituting from 50% to 80% of their fatty acid composition. Because of the importance placed on dietary MUFA, it has been recommended that MUFA intake be as high as half of the total recommended dietary intake of calories from fat (30%) as a means for reducing the risk of coronary artery disease (R. J. Nicolosi, A. F. Stucchi and J. Loscalzo,Chapter 7 in Health Effects of Dietary Fatty Acids, G. J. Nelson, ed., AOCS Press, Champaign, Ill., 1991, pp. 77-82; M. Bockisch in Fats and Oils Handbook, AOCS Press, Champaign, Ill. 1998; K.-T. Lee and C. C. Akoh, Food Rev. Int., 14, 1998, pp. 17-34).
Although scientifically based claims of health benefits derived from dietary MUFAs previously have been asserted for oleic acid, other monounsaturated fatty acids also occur naturally. The most common are 11-eicosenoic acid (C20:1n-9) and 13-docosenoic acid (C22:1n-9), both of which are found in high levels in some oilseed plants such as jojoba and rapeseed. The shorter chain MUFA 9-palmitoleic acid (C16:1n-7) occurs as a minor component (ca. 2%) in olive and cottonseed oils and in trace amounts in a few other commercially available vegetable oils. Palmitoleic acid occurs in somewhat high amounts in animal fat triglycerides such as lard and tallow (up to 5%) and in still higher levels in some fish oils such as sardine oil. The next lower homologue, myristoleic (9-tetradecenoic) acid (C14:1n-5), occurs in minor amounts in animal fat and in butter. The even lower homologue, lauroleic (9-dodecenoic) acid (C12:1n-3), occurs rarely and in small amounts in natural sources.
Several animal fats contain short chain MUFAs in sufficiently high proportions to make them good starting materials for formulating desirable compositions. Chicken and turkey fats, beef tallow, and foot bone oil triglycerides contain C16:1n-7 in amounts of about 4-6% by weight. Some fish oils such as sardine and menhaden may contain as much as 10-16% C16:1n-7. Whale oil is reported to contain above 13% C16:1n-7, and the now unavailable sperm whale oil contained up to 26%. However, these fats and oils as rendered from the natural sources contain undesirably large relative proportions of the long chain fatty acids of the series C20:x and above. The more saturated and higher melting members C20:0, C20:1 and C22:0 have been reported to contribute to the high atherogenicity of peanut oil, a phenomenon comprehensible in light of the teachings of this patent. See F. Manganaro, et al., Lipids, 16, 1981, pp. 508-517. The polyunsaturated and lower melting members C20:2, C20:3, C20:4, C20:5, C22:2, C22:3, C22:4, C22:5, and C22:6 are non-atherogenic or even cardioprotective, but are highly sensitive to free radical oxidation and cross linking reactions because of their polyunsaturation.
The principal source of a dietary vegetable oil which contains appreciable amounts of C16:1n-7 is macadamia nuts. The two species, integrifolia and tetrafolia, contain C16:1n-7 in amounts ranging from 16 to 25% (w/w) of the fatty acids in the oil. However, both also contain about 2% to 4% C20 fatty acids. In addition, the other fatty acids of macadamia nut oil are closely similar in both identity and quantity to those present in olive oil.
Similarly, some natural fats and oils are acceptable starting materials from which to manufacture desirable compositions, that is , an oil enriched in the other selected short chain MUFAs. For example, tallow contains about 0.5% C14:1n-5. It also contains about 1% or more C20 to C22 fatty acids. Butterfat contains very large proportions, up to 3%, of C14:1n-5. However, butterfat has other lipid components, including a large fraction of C4 to C10 fatty acids. The latter are metabolized by a quite different pathway from the C12 and longer fatty acids. Butterfat also contains greater than 2% C20 fatty acids.
In U.S. Pat. No. 5,198,250, food and pharmaceutical compositions containing short chain monounsaturated fatty acids (MUFAs) and methods of using them are disclosed. In particular, as set forth in detail in that patent, MUFA compositions were formulated to produce beneficial improvements in the metabolic processing of lipids or glucose in animals to which the compositions of matter are regularly administered. Beneficial improvements in the metabolic processing of lipids are evidenced by different effects in various tissues. Generally, the metabolic processing of lipids may include any or all steps in the metabolic pathways which include, in part, lipid uptake from dietary sources, hydrolysis, esterification of fatty acids to produce other lipid species, packaging of lipids into lipoproteins, lipid transport, lipid storage in tissues, lipid or lipoprotein cellular uptake, lipid synthesis, enzymatic modification and catabolism, and pathological lipid deposition in arteries, liver, heart and in adipose tissue. As set forth in the disclosure of that patent in detail, regular or systematic administration of the formulated MUFA compositions provide beneficial improvements in metabolic processing.
In 1998, chicken was the most produced and consumed meat in the United States (USDA 1999, publication #LDP-M-55, Economic Research Service, Washington, D.C.). Despite its production and ready availability as a coproduct of chicken production, chicken fat, unlike beef tallow, is usually not used separately in other food or non-food uses. However, animal fats, in general, are of dietary concern because of their relatively high long-chain (C16 and C18 carbon atoms) saturated fatty acid (SFA) content. Chicken fat can be considered a source of MUFA since they constitute 45-50% of chicken fat fatty acids, while tallow contains only 30-40% MUFA (H. Brockerhoff, R. J. Hoyle and N. Wolmark, Biochem. Biophys. Acta, 116, 1966, pp. 67-72; M. Bockisch, in Fats and Oils Handbook, AOCS Press, Champaign, Ill. 1998).
In brief, MUFAs selected from the group composed of palmitoleic acid (C16:1) and its positional isomers, myristoleic (tetradecenoic) acid (C14:1) and its positional isomers and lauroleic (dodecenoic) acid (C12:1), or their mixtures, whether as free acids, salts or esters thereof, are known to provide improvements in the metabolic processing of lipids. The beneficial health effects of the n-3 class of PUFAs, such as 5,8,11,14,17-eicosapentaenoic acid (EPA) and 4,7,10,13,16,19-docosahexaenoic acid (DHA), are well documented. However, natural sources for such MUFAs, such as macadamia nut oil, are in limited supply. Also, natural compositions containing enriched n-3 PUFAs are needed. In order to satisfy the demands for MUFAs and PUFAs, improved methods are needed. Furthermore, new lipid compositions of UFAs containing PUFAs and MUFAs are needed.
This invention is directed to a method of making a lipid composition enriched in unsaturated fatty acid esters from menhaden oil (MO) and partially hydrogenated menhaden oil (PHMO). According to the method, MO or PHMO is solvent fractionated to produce lipid fractions that are enriched in unsaturated fatty acid-containing triacylglycerols. The fractionated lipid composition has an increased amount of unsaturated fatty acid esters and a decreased amount of saturated fatty acid esters compared to their original amounts in the MO or PHMO.
According to one preferred method of the invention, PHMO is solvent fractionated with a solvent, such as acetone, and the fractionation is conducted at a low temperature, preferably below ambient or room temperature, or below the range of 0xc2x0 C. to xe2x88x9215xc2x0 C., and, more preferably, in a range of about xe2x88x9218xc2x0 C. to about xe2x88x9240xc2x0 C. In another form of the method, the oil is liquified and then dry-fractionated over a temperature range of about xe2x88x9210xc2x0 C. to about 35xc2x0 C. during which time liquid and solid phases are formed. In the case of MO, dry fractionation is conducted at about xe2x88x9210xc2x0 C., whereas with PHMO, the dry fractionation temperature is about 30xc2x0 C. The separated liquid phase is then solvent fractionated with a suitable solvent, such as acetone, at low temperatures on the order of about 0xc2x0 C. to about xe2x88x9240xc2x0 C.
The unsaturated fatty acid-containing triacylglycerols enriched fractions produced by the method have significantly increased amounts of PUFAs and MUFAs. For instance, solvent fractionations at about xe2x88x9218xc2x0 to about xe2x88x9238xc2x0 C. produced lipid compositions having about 18% to about 32% by weight more UFAs compared to the original amounts of UFAs in the MO or PHMO. In contrast, saturated fatty acids (SFAs) in the solvent fractionated lipids decreased to about 7% to about 31% by weight of the original SFAs present in the MO or PHMO. In general, the UFAs increased about 5% to about 32% by weight and SFAs decreased about 7% to about 31% by weight for liquid and solid fractions for MO and PHMO. Correspondingly, the MUFAs in the fractionated lipid compositions increased about 0.5% to about 24% by weight of their original amounts; whereas the PUFAs increased about 3% to about 40% by weight for both MO and PHMO, and the SFAs decreased about 5% to about 50% by weight of their original amounts, and the eicosapentaenoic (EPA) and docosahexaenoic (DHA) classes increased about 5% to about 18% by weight of their original amounts.
When the two-step process is used, separation of a liquid phase of the MO or PHMO is required by dry fractionation at ambient temperatures, preferably a range of about xe2x88x9210xc2x0 C. to 35xc2x0 C., prior to solvent fractionation. The two-step process employs less solvent in the solvent fractionation step. MO did not give an isolatable ( less than 2%) solid fraction above 0xc2x0 C. or a liquid fraction below xe2x88x9210xc2x0 C. Similarly PHMO remained mostly liquid above 31xc2x0 C. and solid below 18xc2x0 C.
In summary, novel lipid compositions are produced by the method of this invention. These compositions provide a number of advantages. For example, the content of the PUFAs, MUFAs and EPA and DHA classes in the lipid compositions are increased with a significant decrease of SFAs. An increase of the ratio of the unsaturated to the saturated fatty acids is also provided. The method offers an overall natural product for human consumption to facilitate the metabolic processing of lipids and avoid unwanted lipid deposits.
Other benefits and advantages of this invention will be further understood with reference to the following detailed description and examples.